Lifting-jack



W. E. LOMBARD. LIFTING JACK.

APPLICATION FILED MAR. 26. 1919.

1,352,207. PatentedSept. 7,1920.

2 SHEETS-SHEET 1- w. E. LOMBARD.-

LIFTING JACK. APPLICATION IFILED m mze, 1919.

Patented Sept. 7

2 SHEETSSHEET 2- D- g -ss PATENT; OFF-m WALTER. E. LQMBARD, or ARLINGTON, MASSACHUSETTS.

LIFTmcr-JAck. 4

To all tohom it may concern:

Be it known that I, WALTER E. LoMBARn,

' a citizen of the United States of America,

and a resident of Arlington, in .the county .of Middlesex and Commonwealth of Massachusetts, have invented certain new and useful Improvements in Lifting-Jacks, of

t which the following is a specification.

This invention relates to lifting jacks and particularly that class of jacks known as screw jacks, themain object of the invention being to provide a device of this character which is self-lowering and in whlch the speed of lowering will be automatically the varlous lnstrumentalities of which the invention consists can be controlled.

Another object of the inventlon 1s toprovide a brake mechanism which will. normally prevent the lowering of the load but which may be releasedby the footof the operator when it is desired to lower the jack. A further object of the lIIVGIltlOII is the provision of means whereby the operating parts may be confined in the base of the lift- -ing jack thus-concentrating the preponderw ance of weightnear the bottom of the jack.

The invention consists primarily in ut1l1zing a non-revoluble screw and a rotatable nut, said n'ut' bein'r connection adapted to positivelv rotate 'the.

- 'mitti'ng said nut to reverse direction lowered.

'driven by a driving nut during the raising of the load while 'per freely revolve in the while the 'load is being The invention further-consists in proVid-. ing an auxiliary train of gears adapted to be actuated by the rotation of the revoluble the lowering operation and which train of gears has a sufficiently high ratio of speed reduction to cause its inertia to substantially retard and brake the descent of the jack under its load.

The invention I further consists in pro viding a speed retarding mechanism at the high. speed end of the auxiliary train of gears whereby the speed of the rotatlng nut may be automatically controlled during the lowering operation.

The invention further consists in providing a manually controlled brake mechanism at the high speed e'nd of the auxiliary train of gears adapted to prevent thev lowering of the jack under normal conditions.

The invention further consists in providing a one-way clutch mechanism or slmilar driving connection between the revoluble nut and the low speed end of the auxiliary Specification of Letters Patent.

'tlon one 'trated in v been found to give satisfactory. and reliable train of gears whereby said train will be actuated by the rotation of said nut only during the lowering of the load.

. The invention further consists in certain novel features of construction and arrangement of parts which will be readily understood by reference to the description of the results, although it is to be understood that and organized and the invention is not limited to the precise arrangement and organization of these instrumentalities as herein shown and described, except as required by the scone ofthe appended claims.

' Of the drawings:

Figure 1 represents a vertical section of a lifting ack embodying the principles of the resent invention.

Fig. 2 represents a horizontal same on line 2, 2, on Fig. 1.

F 3 represents a vertical section 3, 3," on Fig. 1.

i2. 4 represents line 4, 4, on Fig. 1.

plan of the on line a horizontal section on F 1g. 5 represents a vertical sbtiim on line v5, 5, on Fig. 2, and

- which is bolted the vertical tubular standard 12. I

Surrounding the standard 12 and movable'endwise thereof is the cylindrical member 13, to the upper end of which is secured a removable cap 14. This cap 14 is provided with a downwardly extending central hub 15 to which is secured a non-revoluble screw 16.

The upper end of the screw 16 is provided with a reducedshank 17 fitted into said hub 15 and retained therein by the locking pin 18.

The cap. 14 is prevented from rotating relatively to the movable cylindrical member 13 by the screw 19 and the said movable Patented Sept. 7, 1920. Applicationfiled March 26, 1919. Serial Iva-288,863.

variously arranged r standard 12.

member 13 is prevented from rotating relatively to the standard 12 by means, of the block 20 mounted on the inner end'of the threaded member 21 and,positioned within the vertical slot 22 in the outer wall of the The opposite ends of the slot 1'22 are closed, having abutments 23, 24 which limit the vertical movement of the cylindrical member 13 in either direction as it is moved relatively to the standard 12.

The standard 12 is provided with an inwardlyextending anrfular flange 25 on s which rests a hardened ring 26 having an annular groove 27 in its upper face.

In the groove 27 are positioned a plurality of balls 28 on which rests another hardenedring 29 secured to and revoluble with the revoluble nut 30.

This nut 30 coacts with the screw 16 and when r ,tated imparts vertical movement thereto. p

The threads of the screw 16 and nut 30 are of sucha pitch asto permit the screw 16 to rotate the nut 30 during the lowering. op-

eration.

The nut 30 is provided with a downwardly'extending tubular portion 31 and is provided near its lower end with a bevel gear 32.

Superimposed upon the gear 32 IS a hardened annular plate 33 having an annular groove 34 in its upper face in which groove are positioned a plurality of balls 35 which are also positioned partially in an annular groove 36 in a hardened plate 37, the upper face of which bears against the shoulder. 38 in the lower enlarged end of the standard 12.

The anti-friction members 28 and 35 permit the nut 30 to freely rotate within the "The operating shaft or spindle 41 is pro- .vided at its inner end with a disk flange 45 having secured to its inner face a plurality of pawls 46 adapted to en age a ratchet 47 pinned or otherwise secure to the gear 39.

The pawls'46 and ratchet 47 are so constructed as to impart a positive movement to the gear. 39 when it is desired to raise the load by means of the operating mechanism 44 and prevent the gear 39 from freely rotating independentlyof said shaft or spin dle 41 when the load is being lowered.

It is obvious therefore that when the operload is being lowered the shaft or spindle will rotate with the gear 39 in a, reverse direction without affecting the operating mechanism 44.

This movement of the gear 39 by means of the operatin mechanism 44 will revolve the gear 32 an nut 30 in a direction relatively to the non-revoluble screw 16 to move said screw upwardly and raise the load.

During the lowering operation the downward movement of the screw 16 will rotate the nut 30 and gear 32 in the reverse direction and it is obvious that at this time the driving gear 39 will freely revolve about the stud 40 without in any manner affecting the shaft 41 and operating mechanism 44,the pawls 46 riding over the teeth of ratchet 47 during this reverse movement.

In the lower end of the tubular portion 31 of the nut 30 and beneath the lower end of will rotate with said nut 30.

Centrally disposed in sa'id'pl'ate 50 and a keyed thereto is the shank 51 of a slidable member 52 having an outwardly extending flange at its lower end between which and the plate 50 is a helical spring '53.

The lower 'end of the-slidable member 52 is provided with a plurality of ratchet teeth normally retained by the spring 53 inengagement with coacting teeth on the upper face of the gear 54.

The teeth on the slidable member 52 and the gear" 54 are" so constructed that during the lifting of the load the slidable member- 52 will freely revolve with the nut 30 withp out effecting the rotation of the gear 54 but as soon as the nut 30 is rotated in the reverse direction during the lowering operation, the teeth will coact to cause said, gear 54 to be rotated by the revolution ofthe nut 30.

The gear is adapted to turn freely upon the stud 55 extending upwardly from thebase 10 in axial alinement with the screw 16. I

The gear 54 meshes with a pinion 55 keyed to the shank 56 of a gear 57 said shank-56 being revolubly mounted in a plate 58 secured to the upper end of the flange 11.

The gear 57 meshes with a pinion 59 also loosely mounted on the stud 55 beneath the gear 54.

This pinion 59 meshes with a gear 60 keyed to the shank 61' of a pinion 62, said shank 61 being revolubly mounted in a bearing in the plate 58.

The pinion 62 meshes with the gear 63 rotatable with the brake disk 64 revoluble about the stud 55 The brake disk 64 is positioned in and closes the upper end of cylindrical chamber formed by the annular fixed flange 65 extending upwardly from the base 10, said flange surrounding and being concentric to the stud 55.-

A brake lever 66 is pivoted at 67 to ears extending outwardly from the flange 11 and its inner end is provided with a friction pad 68" normally retained in engagement with said brake disk 64 by means of a spring" 68 interposed between the flange 11 and a downwardly extending portion 69 of said lever .66.

The outer end 70 of the lever 66 is horizontal and its upper edge rounded over as indicated in Fig. 6.

Resting on this end 70 is the toe end-of a. foot rest 71 pivoted at 72'to the base 10 and having an upwardly extending flange 73 surrounding the heel porti0'n.-

The base 10 is provided with a stop 74 for the rear end of the foot-rest and when the jack is in use the operator places his left foot on the foot rest 71 and normally retains it in contact with the back stop 74. 1

With his left. foot on the foot rest, he can control the operation of the jack, a'slight downward pressure of. the toe releasing the friction padj from contact with the brake disk 64. 1

When the load is being lifted, the friction pad 68 in contact with the brake disk 64 prevents the rotation of any of the gears 55, 57, 59, 60, 62 and 63 it is desiredto lower 40 in the train'between said disk 64 and the one-way clutch 52'54.

When the load has been lifted it'is retained in its elevated position by. means of the brake pad 68 and disk 64 but as soon as the load the operator actu'a'tes the lever 66 to remove-the pad 68 from said disk 64 and the load will immediately force the screw 16' downwardly in the nut 30 thereby causing rotation of saidnut in a reverse direction. This reverse movement of the nut will effect, through the the rotation of the entire train of gears 54,

andalso the rotation of the brake disk 64.

The train of gearing has a sufficiently. high ratio of speed reduction as to cause its inertia to retard and brake the descent of the jackunder its load. It is self evident that owing to. the fact that the brake disk is. applied at the high speedend. of the auxiliary train of gearing,

the descent. of the jack under maximum loads may be perfectly controlled by the operator by means of the brake lever 66 and the lowering operation efl ected withoutjarring or injuring the jack.

To the under face of the brake disk 64 are pivoted weightedlevers 7 5 to the shorter arms 76 of which are pivoted slidable fric- C tion members77- normally held free from for movin said screw endwise' means for P positively actuating sa1d nut in one d1rec-- engagement with the wall of the flange by means ofthe springs 78.

These levers 75- and slidable friction members 77 form an automatic speed' retarder when flange 65. r

When the jack is lowered at a normal coacting with the fix'ed speed the levers will not operate but as soon as the-speed of rotation of the nut 30 exceeds the normal, the weights 79 on thelevers 7 5 will be thrown outwardly by centrifugal action and the .friction members 77 will be forced into engagement with the wall of the flange 65 andthe speed will be reoperating parts near the base is that'the upper end is free from all projecting members and makes it possible to utilize the jack where other forms of jacks could not be used.

Bymeans of the auxiliary train of gears, the lowering ofv the jack may be controlled readily under all conditions.

It is believed that the operation and many advantages of theinventlon will be readily understood without further description.

Having thus described my invention claim 1. In a lifting jack, the combination of, a

non-revoluble lifting screw; a revoluble, nut.

driving mechanism for sa1d nut including tion only; means for preventing end movement' of said nut; and-means for controlling the rotatio" of said nut during the lowering operation? 2. In alifting jack, the combination of a non-revoluble lifting screw; a revoluble nut or moving said screw endwis; drivingmechanism for said nut including means for positively actuating said nutin one direction only; means for preventing endmovement of sai nut; and automatic means for controlling the rotation lowering operation. v

3. In a lifting jack having a chambered base, the combination of a non-revoluble lifting screw; a revoluble nut for; moving said screw endwise tuating said nut in one direction only;*and

.120 driving-mechanism for said nut lneluding means for posltively acmanually controlled means including a revoluble disk" in axial alinement with said screw for-controlling the rotation of said nut during the lowering operation, said disk being rotatable about a fixed stud projecting upwardly from said base.

4? In a lifting jack having-a chambered 115. of-said nut during the base, the Combination of a non-revoluble lifting screw; a revoluble nut for moving said screw endwise; driving-mechanism for said nut including means for positively ac- 5 tuating said nut in one direction only; and automatic and manually controlled means including a revoluble disk in axial alinement with said screw for controlling the rotation I of said nut during the lowering operation, said disk being rotatable about a fixed stud projecting upwardly from said base.

' 5. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut for moving said screw endwise; drivingmechanism for said nut including means for positively actuating said nut in one direction only; brake mechanism normally operating to prevent the lowering of the jack and including a revoluble disk in axial alinement with said screw; and means operable by the foot of the operator for releasing said brake mechanism.

6. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for preventing end movement of said nut; and driving-mechanism for said nut including means whereby said nut may rotate independently sthereof in the reverse direction during the lowering opera- 0 tion.

7. In a lifting jack, the combination of a V non-revolublelifting screw; a revoluble nut therefor; means for preventing end .movement of said nut; an operating shaft; a stud thereon; a nut-driving member on said stud;

and means on saidoperating shaft for positively moving said nut-driving member in one.direction only.

8. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for preventing end move.- ment of said nut; an operating shaft; a stud thereon; a nut-driving member on said stud; a ratchet on said member; and pawls carried by said operating shaft and engaging said ratchet for positively moving said nut-driving member in one direction only.

9. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for rotating said nut; means for preventing end movement of said nut:

and anti-friction. members for taking care of the end thrust of said nut in either direction.

1-0. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means .for preventing end movement of said nut; an operating shaft; and a driving connection between said shaft and 'n11t having provision for positively rotating said nut v,in one direction and permitting its rotation in a reverse direction relatively to said operating shaft.

11. In a. lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for positively rotating said nut in one direction and permitting free movement thereof in a reverse direction; a

fixed cylindrical member alined with said nut; an automatic speed retarding mechanism w1th1n said cylindrical member and including a revoluble disk closing the upper fixed cylindrical member alined with-said nut; an automatic speed retarding-mechanism within said cylindrical member; a train of gears actuated by the rotation of said nut during the lowering operation and a revoluble disk carrying said speed retarding mechanism and actuated by said train of gears.

13. In a lifting jack the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for positively rotating said nut in one direction and permitting free movement'thereof in a reverse direction; a fixed cylindrical member alinedwith said nut; an automatic speed retarding mechanism within said cylindrical member; a train of gears actuated by the rotation of said nut during the lowering operation; a

revoluble disk carrying said speed retarding mechanism and actuated by said train of gears; and a friction brake member coacting with said disk.

14. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for positively rotating said nut in one direction and permitting free movement thereof in a reverse direction; a fixed cylindrical memberbeneath and alined with said nut; an automatic speed retarding mechanism within said cylindrical member and including a revoluble disk closing the upper end of said chamber; and means actuated by said nut during the lowering operation for rotating said speed retarding mechanism. I

15. In a lifting jack, the, combination of a non-revoluble lifting screw; a revoluble nut therefor; means for positively rotating.

said nut in one direction and permitting free movement thereof in a reverse direction; a fixed cylindrical member alined with said nut; an automatic speed retarding mechanism within said cylindrical-- member; a train of gears actuated'by the rotation of said nut during the lowering operation; a revoluble disk carryingsaid speed retarding mechanism and actuated by said train of gears; and a manually controlled friction brake member, coactingwith said disk.

16. In a lifting jack, the combination of I said nut in one direction and permitting free a non-revoluble'lifting screw; 'a revoluble nut therefor; means for positively rotating movement .thereof in a reverse direction; a non-revoluble stud beneath and in anal v alinement with said screw. but separated therefrom; a fixed cylindrical member surrounding said stud; an automatic speed retarding mechanism revoluble about said stud within said cylindrical member; and means actuated by the rotation of said nut. during the lowering operation for rotating said speed retarding mechanism.

' 17. In a lifting jack, the combination of anon-revoluble lifting screw; 1a revoluble nut therefor; means for positively rotating said nut in one direction and permitting free movement thereof in a reverse direction; anon-revoluble stud beneath and in axial alinement with said screw but separated therefrom; a fixed cylindrical member surrounding said stud; an automatic speed retarding mechanism revoluble about said' stud within said cylindrical member; a revoluble disk closing the upper end of said cylindrical member and supporting said speed retarding mechanism; and means actuated by the rotation of said nut during ghek lowering .operation for rotating said 1s e 18. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for positively rotating said nut inone direction and permittingfre'e movement thereof in a reverse direction; a non-revolublestud beneath and in axlal alinement with said screw but separated I f voluble disk closing the upper-end of said free movement thereof in'a revesre direction; -a fixed stud extending-upwardly from the" therefrom; a. fixed cylindrical member surrounding said stud; an automatic speed retarding mechanism revoluble about said stud within said cylindrical member; a recylindrical member and supporting said speed retarding mechanism; means actuated 5 ing operation for rotating said disk; and-a by .the rotation of said nut during the lowerpivoted brake member normally coacting with said disk.

19. In a lifting-jack, the combination ofa non-revoluble lifting screw; a revoluble nut therefor; means for positively rotating said nut in one direction and permitting base of the jack beneath and in axial a linement with saidscrew but separated therefrom; a fixed cylindrical member surrounding said stud; an automatic speed retarding mechanism revoluble about said stud within said cylindrical member; a revoluble disk closing th upper end of said cylindrical member and supporting said speed retarding mechanism; means actuated by the'rotation of said nut during the lowering operation for rotating said disk and. a ,springactuated pivoted brake member normally coactingv with said disk. 1

20. Ina lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for preventingend movement of said nut; means for POSItIlVLIy ment of said nut; means for positivelyro tating said nut in one direction and permitting free movement thereof in a'reverse direction; a fianged disk secured to the upper end'of said screw and movable vertically therewith;- a cylindrical member secured to the flange of said disk; and a non-movable cylindrical nut-supporting standard ill-" closed within said movable cylindrical member.

22. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; means for preventing end movement of said nut;.meansfor positively rotating said nut in dne directionand permitting free movement thereof in a reverse di-' rection a cylindrical member secured to and movable verticallywithsaid screw; a nonmovable cylindrical nut-supporting standard inclosed within said movable cylindrical member and provided with a vertical slot closed at opposite ends; and a block carried I bysaid movable member and positioned 23. In a lifting jack, the. combination of I within said 'slot.

a chambered base; a cylindrical {standard fixedly secured to saidba'se; a vertioallymovable member surrounding said. standard; a non-revoluble screwsecured toand movable with said movable, member; speed retarding mechanism within the chamber of said base; a train of gears for actuating said 'speedretar ding mechanism also within said lifting screw when rotating in one direction and-saidtrain of gearing when rotating in" chamber; a revolublenut for actuating said the reverse direction; and means for posipermitting free movement thereof in a reverse direction. I 1 24. In a lifting j ackfthe combination of a tively. rotatingsaid nut in'one-direction and Y chambered base; a'cylindrical standard" fixedly secured to said base; a vertically movable member surrounding said standard; a

non-revoluble screw secured to and movable with said movable member; brake mechaj nism and speed retarding mechanism with in thechamber ofsaid base; va train of .130

s a s a mee ing-sa d brake mechanism and speed retarding mechanism also within said chamber; a revoluble nut for actuating said lifting screw when rotating in one direction and said train of gearing when rotating in the reverse direction; and means for positively rotating said nut in one direction and permitting free movement thereof in a reverse direction. I

25. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut for moving said screw endwise a fixed cylindrical standard; anti-friction bearings therein for said nut; driving mechanism for said nut including means for positively actuating said nut in one direction only mechanism for controlling'the rotation of said nut; and means whereby said controlling mechanism is actuated only during the lowering operation.

26. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut for moving said screw endwise a fixed cylindrical standard; bearings therein for said nut and preventing end movement thereof; driving mechanism for said nut including means for positively actuating said nut in one direction only; automatic mechanism for controlling the rotation of said nut; and means whereby said controlling mechanism is actuated by said nut only during the lowering mechanism.

27. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut for moving said screw endwise; driving mechanism for said nut including means for positively actuating said nut in one direction only; a brake mechanism including a revoluble brake disk; and means whereby said disk is rotated by said nut only-during the lowering operation.

28. In a lifting jack, the combination of anon-revoluble lifting screw; 1 revoluble nut for moving said screw endwise; driving mechanism for said nut 1nclud1ng means for positively actuating said nut in one direc-'.

tion only; automatic and manually con trolled means for controlling the rotation.

of said nut during the lowering operation; and mechanism actuated by the reverse 'movement of the nut for placing said controlling means in operation.

29. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; driving mechanism therefor; a fixed cylindrical member; an automatic speed retarding -mechanism within said cylindrical member; means for rotating said speed retarding-mechanism; and a one-way clutch between said nut and rotating means and adapted to be disengagedby end movement of one part thereof.

'30. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; driving mechanism therefor; a fixed cylindrical member; an automatic speed retarding mechanism within said cylindrical member; a train of gears; a revoluble disk carrying said speed retarding mechanism and actuated by said train of gears; and a one-way clutch between said nut and train of gears and adapted to be disengaged by end movement of one part thereof.

31. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; driving mechanism therefor; a fixed cylindrical member; an automatic speed retarding mechanism within said cylindrical'member; a train of gears actuated by the rotation of said nut during the lowering operation; and a revoluble disk carrying said speed retarding mechanism and actuated by said train of gears.

32. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; a fixed cylindrical standard; bearings therein for the opposite ends of said nut and preventing end movement thereof; driving mechanism therefor; a fixed cylindrical member; an automatic speed retarding mechanism within said cylindrical member; and means actuated by said nut during the lowering operation for rotating said speed retarding mechanism.

33. In-a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut therefor; driving mechanism therefor; a fixed cylindrical member; an automatic speed retarding mechanism within 'said cylindrical member; a train of gears including an initial gear having ratchet teeth; a revoluble disk carrying said speed retarding mechanism and actuated by said train of gears; and a toothed member carried by and movable endwise relatively to said nut and adapted to engage said ratchet teeth during the lowering operation.

34. In alifting jack the combination of rotation of said nut during the lowering operation for rotating said disk. I

35. In a lifting jack, the combination of a chambered base; a cylindrical standard fixedly secured to said base; a vertically movable member surrounding said standard; a non-revoluble screw secured to and movable with said movable'member; speed retarding mechanism within the chamberof said base; a' train of gears for actuating said speed retarding mechanism also Within said chamber; a revoluble nut for actuating said lifting'screw; means for positively rotatingsaid nut in one direction; and means interposed between nut and train of gears whereby said train will be actuated only by the rotation of the nut in a reverse direction during the lowering operation.

36. In a lifting jack, the combination ofa chambered. base; a cylindrical standard fixedly secured to said base; a vertically movable member surrounding said standard; a non-revoluble screw secured to and movable with said movable member; brake mechanism and speed retarding mechanism within the chamber of said base; a train of gears for actuating said brake mechanism .and speed retarding mechanism also within said chamber; a revoluble nut for actuating said lifting screw; means for positively rotating said nut in one direction and permitting free movement thereof in a reverse direction; and a one-way clutch between said nut and train of gears one part of said nut being movable endwise and adapted to make a driving connection between said train and nut during the lowering operation.

37. In a lifting jack, the combination of a base; a cylindrical standard fixedly secured to said base; a vertically movable membersurrounding said standard; means preventing the rotation of said vertically movable member; a non-revoluble screw secured to and movable with said movable member; a revoluble nut for actuating said lifting screw; means within said standard for preventing end movement of said nut while permitting the free rotation thereof; means mounted on said base for rotating the nut to lift the load; and means within said base actuated by the rotation of the nut in a reverse direction during the lowering operation for retarding the speed of lowering and preventing it from exceeding a predetermined limit.

38. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut for moving sald screw 'endwlse and havlng ed to be engaged by the teeth of said movable member when the nut is rotated in a reverse direction thereby effecting the op eration of said speed controlling mechanism.

39. In a lifting jack, the combination of a non-revoluble lifting screw; a revoluble nut for moving said screw endwise and having at its lower end a cylindrical portion; a bevel geaf secured to said cylindrical portion; a driving gear meshing with said bevel gear and adapted to actuate said nut in one direction only; a speed retarding mechanism in the base of the jack for controlling the rotation of said nut during the lowering operation, said mechanism being independent of and separated from. said driving gears; a manually controlled brake for normally preventing the operation of said speed controlling mechanism; a train of gears for actuating said speed controlling mechanism the initial gear of which is alined with said screw and provided withengaging shoulders; and a reciprocating member in said cylindrical portion of the nut having shoulders adapted to engage the shoulders on saidgear and actuate said speed controlling mechanism only when the nut is rotating in a reverse direction.

Signed by me at 4 Post Oflice Square, Boston, Mass, this 25th day of March, 1919.

' WALTER E. LOMBARD. In presence of NATHAN C. LoMBARD,

MAZIE W. KIMBALL. 

